‘SUPERMANG’ L67 BUILD
The Carnage boys throw a blown 3.8-litre V6 into an unsuspecting VN Berlina
WHEN it comes to engine swaps these days, it always seems to be ‘LS this’ or ‘Barra that’, and probably for good reason. Both engines are capable of some pretty amazing horsepower on a budget, and at Carnage HQ, we’ve certainly done enough of them to know.
Yet we discarded both those ideas when it came to repowering our new VN Berlina project car, which we’ve nicknamed Supermang. Our plan is to boost a 3.8-litre V6 into a Barra-killer and slip it into a relatively lightweight VN. Some may ask why we didn’t just whack a turbo on the standard VN V6, but I’ve done that before, and while the result was a stout 11-second sleeper, I’ve always wanted to try it with the much stronger factory-supercharged V6.
Finding an engine was simple enough. We bought a ‘Gumtree Special’ VX Commodore for $500 from a Dandenong front yard. It was missing both driver’s-side doors and smelled like dogs had been living inside, but it was an S-pack and it had the right engine: the L67 supercharged six.
We’ve been kicking around the idea of doing a blown L67 project for a few years. They’re a tough little donk and capable of some decent power. They differ from the standard L36
Ecotec engine in a few key areas – namely the conrods, cylinder heads and, of course, the Eaton M90 supercharger.
We’ve seen Drag Challenge regular Josh Grant complete four DCS with his turbo L67powered VB Commodore on a stock bottom end, and he ran high nines last time out. There are even regulars at Calder Park running into the eights with built L67 engines.
To kick things off, we put both the VX and the VN on the Maxx Performance dyno. With only 117,000km on the clock, the VN V6 was pretty decent, producing 98.5rwkw (132rwhp). Not earth-shattering, but solid enough. Now
according to the seller, our L67-powered VX was supposed to have only 180,000km under its belt, but a service sticker showing 409,000km has thrown that into doubt. We gave it some fresh Valvoline and dropped it on the dyno, and with just 6psi of boost on board, it produced 131rwkw (175.5rwhp). So both engines were basically on the money.
Swapping the L67 into the VN would make for a healthy upgrade, especially with a free-flowing exhaust and some intake mods, but we had a bit more planned than that. Originally we wanted to ditch the blower and go straight to a turbo upgrade, but our Carnage Youtube fans seemed interested in seeing how much power we could extract from the L67 in supercharged form, so we gave the guys at Mace Engineering a call and they sent out a bunch of parts.
There are two schools of thought when it comes to L67 modifications. You’ve got the guys who concentrate on externals with pulley upgrades, high-ratio rockers and sometimes intercoolers. Then there are the guys who go all-out – and that is us.
We tore the engine out of the VX and ripped it down to a short block to upgrade the rod bolts, MLS head gaskets and metal intake gaskets. We gave the heads a clean-up and had a local shop shave the decks and do a valve job before we reassembled them with heavy-duty springs and titanium retainers. To work the valves, we went with a Mace Engineering Stage Three cam made by Crow Cams. It’s 214/224@0.050 and 0.564/0.534in lift with standard-ratio rockers. Not a massive cam by any measure, but certainly bigger than stock. We also fitted new lifters and a new timing chain.
Up top, we’ve gone for a 3.2-inch supercharger pulley on a Mace Engineering hub adapter, which will allow for easy pulley upgrades in the future. That should be good for 12psi, and we’ve used an LS1 throttlebody adapter and ditched
the factory VX Commodore airflow meter for an easier engine swap.
On the fuel side of things, we’ve got 1100cc Raceworks E85 injectors and a capable fuel system also supplied by Raceworks. We’re using one of their pumps in the factory tank to feed a surge pot with another high-flow E85 pump and Teflon lines throughout so we don’t end up smelling of E85 every time we drive the car.
From experience, we know E85 and Roots blowers go together like ham and cheese, and with double the boost, the ethanol will help combat intake temps.
A Haltech Sport GM ECU takes care of engine management duties. It's a plug-and-play unit that attaches straight to the factory VN harness. We plugged it into the stock VN engine and found a couple more horsepower, so we know the set-up works, but it’ll really come into its own when we start feeding the little V6 some boost. The Haltech ECU also has the ability to control a few extra inputs and outputs and a CAN bus connection.
We’ve used Tuff Mounts to help secure the L67 and Pacemaker headers to get the gasses out. Being a non-standard fitment – the L67 was only available in Vs-and-later cars – we might have to make a few adjustments to the headers. The lower deck height of the L67 moves the headers down in the engine bay, and the small collectors on the VS Commodore headers we’re using will have to be cut off and enlarged. Pacemaker even sent us some collectors already flared for three primary pipes to help out.
On the transmission side of things, were going to stick with the TH700 from the VN. It’s a bit stronger than the 4L60E that was behind the L67, and there are plenty of aftermarket parts to help out. We will also stick with the factory 3.08-geared, 28-spline Borgwarner, but plan to fit a locker centre. Once we get some track time, we will assess the gear ratio and work out what the car needs.
As we go to print, we’ve bolted the refurbished L67 into the VN but haven’t fired it up yet. The plan is to dyno it at 12psi; if that goes well we will set things up to 19psi or so and fit a Mace Engineering air-to-air intercooler. If any race tracks are open by then, we’ll also send it down the quarter-mile.
Ultimately, we’d love our L67-powered VN to go deep into the 11s in supercharged form. Then we’ll switch it over to turbo and wind the boost up to 25psi or so to hopefully end up in the 10-second zone. It’ll need somewhere in the vicinity of 450-500rwhp to do the job, and we hope to give it a solid thrashing at Drag Challenge later in the year. If an asteroid or supervirus hasn’t killed us all by then, that is.